Thanks for your inputs.
I tried to program the ESCs with a programming card.
If I set control frequency to 22KHz then the ESCs will calibrate both with PWM set 400 and 4000.
But with the last one they will not arm.
A problem I can see with that setting is ESCs becoming warm.
I programmed brake on, always with the programming card and now I feel the braking effect.
I guess that if min and max PWM are set at 125 and 250 it should work as Oneshot125 (syncronized pulse), just refreshed only at 400Hz and not at 4000Hz. Am I completely out of track?
The motors response seems good anyway.
Now it's slope time ...